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Physicists have discovered a new type of analog quantum computer that can solve complex physics problems that the most powerful digital supercomputers can't solve.

A new study published in the journal Nature Physics by scientists from Stanford University in the US and University College Dublin (UCD) in Ireland has shown that a new type of highly specialized analog computer with quantum elements in its circuits can solve advanced tasks. . . of quantum physics, which did not exist before. If upgraded, such devices could shed light on some of the most important unsolved problems in physics.

For example, scientists and engineers have long wanted to better understand superconductivity because existing superconducting materials, such as those used in MRI machines, bullet trains and energy-saving long-distance networks, currently only work at very low temperatures. , limiting widespread use. The holy grail of materials science is finding materials that have superconductivity at room temperature, which will revolutionize their use in many technologies.

Dr Andrew Mitchell is a theoretical physicist at the UCD Center for Quantum Engineering, Science and Technology (C-QuEST), UCD School of Physics, and co-author of the paper.

He said: "Some problems are too complex for even the fastest digital classical computers to solve. An important example is the detailed modeling of complex quantum materials such as high-temperature superconductors; such calculations are beyond our current capabilities. Realistic models are required to simulate properties. "Exponential Computing Time and Memory Requirements”.

“However, technological and engineering advances that have led to the digital revolution have resulted in an unprecedented ability to control matter at the nanoscale. This has allowed us to build specialized analog computers called "quantum simulators" that solve precise models in quantum physics. , exploiting the properties of quantum mechanics inherent in its nanoscale components, has developed analog devices with quantum components that can solve some of the problems of quantum physics."

The architecture of these new quantum devices consists of a metal-semiconductor hybrid embedded in a nanoelectronic circuit developed by researchers at Stanford, UCD and the Department of Energy's SLAC National Accelerator Laboratory (Stanford). Stanford's Experimental Nanotechnology, led by Professor David Goldhaber-Gordon, built and operated the device, while UCD's Dr Mitchell did the theory and modelling.

Professor Goldhaber-Gordon, a researcher at Stanford's Institute for Materials and Energy Science, said: "We always create mathematical models that we hope will capture the essence of the phenomenon we are interested in, but if we think so, it is correct.", often within a reasonable time. cannot be resolved."

With the quantum simulator, 'we have a handle that we've never had before,' says Professor Goldhaber-Gordon.

Why analog?

According to Goldhaber-Gordon, the basic idea behind these analog devices is to create some kind of hardware analog of the problem you want to solve, rather than writing computer code for a programmable digital computer. For example, suppose you want to predict the motions of planets in the night sky and the timing of eclipses. You can do this by building a mechanical model of the solar system, where one turns a knob and interlocking spinning gears represent the motions of the moon and planets.

In fact, this process was found in an ancient shipwreck near a Greek island that is over 2,000 years old. This device can be considered as one of the first analog computers.

Until it exploded, the analog machine of the 20th century. They were used until the late 20th century for mathematical calculations that were too complex for the most advanced digital computers of the time.

But to solve the problems of quantum physics, the device must have quantum components. The new quantum simulator architecture consists of electronic circuits with nanoscale components whose properties are governed by the laws of quantum mechanics. It is important to note that many of these components can be created, each of which functions essentially the same as the others.

This is crucial for analog simulations of quantum matter, where each electronic component of the circuit is a substitute for a simulated atom and "behaves like an artificial atom". Just as different atoms of the same type in a substance behave in the same way, so the different electronic components of an analog computer must behave in the same way.

The new design therefore offers a unique way to scale the technology from single devices to large networks capable of simulating quantum matter. The researchers also showed that new microscopic quantum interactions could be implemented in such devices. The work is a step toward developing a new generation of scalable solid-state analog quantum computers.

The first quanta

To demonstrate the power of analog quantum computing with their new quantum simulator platform, the researchers first analyzed a simple circuit with two quantum elements connected to each other.

The device simulates a model of two atoms connected by a special quantum interaction. By controlling the electrical energy, the researchers were able to create a new state of matter where the electrons appear to have only 1/3 of their normal electrical charge, the so-called 'Z3 parafermion'. These elusive states have been proposed as the basis for future topological quantum computing, but have never been created in electronic devices in the laboratory.

'By scaling the two-material quantum simulator to the nanoscale, we hope to be able to simulate much more complex systems that modern computers cannot handle,' said Dr. Mitchell. "This could be the first step towards finally solving the most amazing mystery of our quantum universe."